Hard disk drives (HDDs) are used in almost all computer system operations. In fact, most computing systems are not operational without some type of hard disk drive to store the most basic computing information such as the boot operation, the operating system, the applications, and the like. In general, the hard disk drive is a device which may or may not be removable, but without which the computing system will generally not operate.
The basic hard disk drive model includes a storage disk or hard disk that spins at a designed rotational speed. An actuator arm is utilized to reach out over the disk. The arm carries a head assembly that has a magnetic read/write transducer or head for reading/writing information to or from a location on the disk. The transducer is attached to a slider, such as an air-bearing slider, which is supported adjacent to the data surface of the disk by a cushion of air generated by the rotating disk. The transducer can also be attached to a contact-recording type slider. In either case, the slider is connected to the actuator arm by means of a suspension. The complete head assembly, e.g., the suspension and head, is called a head gimbal assembly (HGA).
In operation, the hard disk is rotated at a set speed via a spindle motor assembly having a central drive hub. Additionally, there are tracks evenly spaced at known intervals across the disk. When a request for a read of a specific portion or track is received, the hard disk aligns the head, via the arm, over the specific track location and the head reads the information from the disk. In the same manner, when a request for a write of a specific portion or track is received, the hard disk aligns the head, via the arm, over the specific track location and the head writes the information to the disk.
Over the years, the disk and the head have undergone great reductions in their size. Much of the refinement has been driven by consumer demand for smaller and more portable hard drives such as those used in personal digital assistants (PDAs), MP3 players, and the like. For example, the original hard disk drive had a disk diameter of 24 inches. Modern hard disk drives are much smaller and include disk diameters of less than 2.5 inches (micro drives are significantly smaller than that). Advances in magnetic recording are also primary reasons for the reduction in size.
Another advancement to the hard disk drive is the use of smaller components. For example, by reducing the read/write tolerances of the head portion, the tracks on the disk can be reduced in size by the same margin. Thus, as modern micro recognition technology is applied to the head, the track size on the disk can be further compressed thereby enabling more tracks to be included on the disk, resulting in the disk having an increase data storage capacity.
As part of the production process of hard disk drives, multiple tests are typically run on each Head Gimbal Assembly (HGA) to determine whether it satisfies performance specifications and/or size tolerances. Specifically, the test modules used in current HGA testing consist of utilizing fixed test sequences. Furthermore, to address challenges of reduced head performance margin with increased areal density, the HDD industry has moved from fixed TPI/BPI format and flying-height (FH) to adaptive HDD format by varying TPI/BPI and tunable FH by using Thermal Fly-height Control (TFC). However, current test module with a fixed test sequence has severe limitations to simulate HDD operation, resulting in either poor test efficiency (e.g., poor HDD or HGA yield) or longer test time.
One of the conventional techniques to decrease test time and the expense of testing is to reduce the HGA testing to the essential testing that protects the HDD yield. However, this typically results in the exclusion of other testing that provides information about the testing process, which can be desirable for research and development.
Another issue with fixed test sequence is that dynamic electrical testing (DET) serves various purposes, requiring varying test modules. The current approach is to direct parts with different testers with varying test modules, which increases tester investment and creates additional requirement in parts logistics.